Shadows fill the memories(a fairy tail fanfic: book one!)

Natsu wakes up in the fairy tail infirmary. But his only memories are:
Name-Nastu Dragneel
Magic-fire dragon slayer and demon heart magic
He looses his memories of fairy tail but gains the power of a demon! And with zeref in his head, what kind of road will Natsu take? Read to find out!!!!!

I don't not own fairy tail or any of these characters besides the ones I make up if any.